Anchor Size Calculator
Enter your boat's length, the anchor type, whether the boat is heavy or exposed to strong winds, the anchoring depth and the rode type. The calculator gives a starting anchor weight and the rode length to carry.
- Anchor weight
- Rode length
- Chain lead
Always check the anchor maker's chart, which may recommend a different size.
A modern anchor of about 1 lb per foot of boat suits most boats. A 30 ft boat takes about a 30 lb plough, claw or new-generation anchor, or about 18 lb for a fluke anchor. Anchoring in 15 ft of water with rope and chain at 7 : 1 scope needs about 128 ft of rode.
Anchor size chart
Rule of thumb. Search for a boat.
| Boat (ft) | Claw or plough (lb) | Fluke (lb) | Heavy boat, claw (lb) |
|---|---|---|---|
| 15 | 15 | 9 | 18 |
| 20 | 20 | 12 | 24 |
| 25 | 25 | 15 | 30 |
| 30 | 30 | 18 | 36 |
| 35 | 35 | 21 | 42 |
| 40 | 40 | 24 | 48 |
| 45 | 45 | 27 | 54 |
| 50 | 50 | 30 | 60 |
Pounds.
Boat length and anchor
Claw anchor. Slide the boat length.
The boat is drawn anchored with its rode.
How to size an anchor
Boat to anchor. Step through it.
Length
Boat.
Back down on the anchor gently with the engine to set it before you rely on it.
Claw, fluke or new-generation
Anchor types. Compare them.
All round.
Light.
Modern.
Fluke anchors hold well in sand and mud but can struggle to reset if the wind shifts.
Before you anchor
Anchor checks. Tick each item.
Tick each item as you go.
Mark the rode every 25 ft so you know how much is out.
What you get
Anchor sizing. Each tile explains one result.
Pounds.
Length.
Lead.
Ratio.
Added.
Holding depends on the seabed as much as the anchor.
Frequently Asked Questions
No question matches that search.
What size anchor do I need?
About one pound per foot of boat for a claw or new-generation anchor.
What size anchor for a thirty foot boat?
About thirty pounds for a claw anchor.
How much anchor rode do I need?
Seven times the depth plus bow height for rope with chain.
What is anchor scope?
The ratio of rode length to the depth plus the height of the bow.
How much chain should I use?
About one boat length of chain with a rope rode.
Is a heavier anchor better?
Usually, yes. Size up when between sizes.
What anchor is best for sand?
Fluke and new-generation anchors both hold well in sand.
Sleep well at anchor
Carry the right anchor and enough rode for your boat, and you stay put when the wind picks up.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.